mtab is not a problem anymore. On Arch, /etc/mtab is just a symlink to /proc/self/mounts.
As for the recovery partition, you don't need the split for that, either. Just have a live system on the recovery partition that mounts the normal root FS. Then you can chroot into there for recovery tasks.
Right, that seemed to be the mtab solution Debian were angling toward. I think there were some odd edge cases where it didn't behave well, though I don't recall what those were. Perhaps the ability to specifically edit the contents to allow fixing of fubared mounts -- almost certainly loopback or NFS, both of which get quite twitchy at times.
I don't recall my precise thinking on a clean root vs. /usr split on the recovery partition, though it may have avoided some confusion over binaries. Or perhaps that you could mount the /usr partition itself independently if you wanted, assuming primary root was hosed.
Not being able to mount a separate /usr would negate that option.
Bind-mounting does give you some options. Still doesn't help if root's hosed.
And it wasn't an option when I'd first come up with this clever scheme.
One of my current challenges with Linux is identifying which information/education of mine is wholly outdated. This will happen to you in time as well....
As for the recovery partition, you don't need the split for that, either. Just have a live system on the recovery partition that mounts the normal root FS. Then you can chroot into there for recovery tasks.